1. Field of the Invention
The present invention relates to the manufacture of films or sheets containing a polymeric substance, and more particularly, to a heat sink sheet which efficiently dissipates heat by being interposed between a heat sink such as an aluminum cooling fin and a heat source of electronic equipment such as a power transistor, a high-density integrated circuit and a plasma display panel (PDP) in such a manner as to fill the gap between the heat sink and the heat source.
2. Description of the Related Art
In recent years, electronic equipment has become higher and higher in performance and smaller and smaller in size, so that electronic parts such as semiconductors are becoming higher in density and function. As the density and function of the electronic equipment become higher, the electronic parts themselves generate a larger amount of heat. If no measures are taken against such heat, the electronic parts are degraded in quality and damaged. It is, therefore, necessary and indispensable to use an apparatus or a mechanism for efficiently removing heat generated from the electronic parts.
The existing method for removing heat generated from a heat source in electronic equipment is to interpose a heat sink material between an aluminum cooling fin and a heat source of electronic equipment. The heat sink material used in this method is a silicone heat sink grease, a silicone heat sink sheet, an acrylic-containing pressure sensitive adhesive sheet, an urethane-containing pressure sensitive adhesive sheet or the like. These heat sink materials are of the type in which a filler of high heat conductivity is blended with a soft polymeric material.
However, the above-described conventional heat sink material using a silicone heat sink grease, a silicone heat sink sheet or the like is superior in heat sink performance because the heat sink material is charged with a heat sink filler of high heat conductivity in a large amount. However, the heat sink material has no function of a pressure sensitive adhesive, and has the problem that the aluminum cooling fin and the heat source must be secured by using separate means such as screws. In addition, there is another problem that the silicone heat sink sheet is difficult to secure to a heat source such as a CPU, an aluminum cooling fin or the like during the process of manufacturing electronic equipment.
On the other hand, the acrylic-containing pressure sensitive adhesive sheet and the urethane-containing pressure sensitive sheet are superior in securing performance to the silicone heat sink grease or the silicone heat sink sheet. However, the acrylic- and urethane-containing pressure sensitive sheets are remarkably low in heat conductivity compared to the silicone-containing heat sink material and has the problem that they cannot fully conduct heat to aluminum cooling fins and cannot be used in portions which generate a large amount of heat.